# Thread: The burn mark problem

1. Originally Posted by Jack_
Can you explain this?

Are you saying that light in fact has an infinite number of paths in reality based on the frame?
Newtonian physics says that the spatial path of anything is frame dependent.
Bounce a ball.
In the rest reference frame of Earth's surface, it goes down and up, a total distance of about a metre.
In the rest reference frame of the Sun, it goes about 30km, and the shape of the path depends on the your latitude and the time of day.

Wow, indeed.

2. Originally Posted by Pete
So the laser only goes as far as x? Or does it continue burning the path indefinitely?

Is that time is on the vertical axis? If so, why is O' stationary?
If not, then how are you going to apply a Lorentz transform?
you have enough information here to decide this problem.
You claimed you understood LT better than I do.

You explain it.

If you admit you do not understand it, then I will help.

3. Originally Posted by Pete
Newtonian physics says that the spatial path of anything is frame dependent.
Bounce a ball.
In the rest reference frame of Earth's surface, it goes down and up, a total distance of about a metre.
In the rest reference frame of the Sun, it goes about 30km, and the shape of the path depends on the your latitude and the time of day.

Wow, indeed.

We are taliking about the light path and that SR claims that is absolute.

4. Originally Posted by Jack_
Oh? So exactly where is this point?
A point in spacetime (an event) is not the same as a point in space (a location).

The emission location moves differently in different reference frames; it is frame dependent. Things that stay at that location in one frame might not stay there in all frames.
The emission event is well defined in all frames of reference - anything that occurs at that event in one frame will occur at that event in all frames.

5. Originally Posted by Pete
A point in spacetime (an event) is not the same as a point in space (a location).

The emission location moves differently in different reference frames; it is frame dependent. Things that stay at that location in one frame might not stay there in all frames.
The emission event is well defined in all frames of reference - anything that occurs at that event in one frame will occur at that event in all frames.
Good, I want you to measure this point in two frames with a common co-location of light emission.

I want the absolute values.

Recall, you claimed you know SR better than I do.

Oh, if SR does not know the absolute light path, then the clock synchroinzation method falls.

Yes, if that falls, then since LT is based on that absoluteness, then LT falls.

6. Originally Posted by Jack_
We are taliking about the light path and that SR claims that is absolute.
This is precisely the task. SR does not claim that the light path is absolute, and this is not a physical contradiction.

You said:
Can you explain this?

Are you saying that light in fact has an infinite number of paths in reality based on the frame?
Yes I am, just as a bouncing ball has an infinite number of paths in reality based on the frame.

Then, Einstein says the light path is "free from contradictions" for the clock sync.
Perhaps you are confusing a spatial path with a worldline (the line on a Minkowski spacetime diagram)?

Yes, the clock synchronisation procedure is free of contradictions, and a frame dependent spatial path does not imply any contradiction.

How do you have a light path length of many values and yet at the same time it is free from contradictions?
In exactly the same way as you can claim that the length of the path of a bouncing ball has many values and yet at the same time it is free from contradictions.

Can you explain this absoluteness of SR?
What absoluteness? We're talking about values that are frame dependent, not absolute.

But, what you are really saying is that the light path has many "real" emission points divergent in space.
Yes, just like the path of a bouncing ball has many real emission points divergent in space.

7. Originally Posted by Pete
This is precisely the task. SR does not claim that the light path is absolute, and this is not a physical contradiction.

In accordance with definition the two clocks synchronize if

tB - tA = t'A - tB

We assume that this definition of synchronism is free from contradictions, and possible for any number of points; and that the following relations are universally valid:--

http://www.fourmilab.ch/etexts/einstein/specrel/www/

Can you explain why "free from contradictions" is not absolute?

In logic, that means a logical truth.

8. Jack_:

That's the first time I've heard anybody say that.
so what
So, since I am highly educated about relativity and it seems a little strange to me that you are using terminology that I have never come across in relation to relativity.

What do you mean when you say two frames are co-located? Recall that a reference frame extends throughout the whole of space.
I mean the same thing as is the case when Einstein with his R of S experiment claimed two frames were co-located.
Can you please post an extract of a reference where Einstein claims two frames are co-located?

No. The emission point of a light pulse, as I explained to you, is a fixed point in spacetime. It does not move.
Oh? So exactly where is this point?
We will need it because SR contends that emission point is the one used to decide t = d/c for a multitude of frames.

I want you to explain this.
Ok. No problem.

You have to be careful in distinguishing events and objects from coordinate systems.

Here's a simple analogy: Put your chair somewhere in the middle of the room you're in, but not at the centre of the room. Now, my question is: where is the chair, precisely?

One answer (A) might be: "The chair is 2 metres from the west wall and 1.3 metres from the North wall."

Another answer (B) might be: "The chair is 3 metres from the east wall and 3.7 metres from the South wall."

Suppose the room is 5 metres by 5 metres in size.

Next question: did the chair move between answers (A) and (B)? The answer, as you should be able to see, is "No". The chair stayed in exactly the same position. What happened was that the coordinate system used to specify the chair's location moved, or to put it another way (A) and (B) use two different coordinate systems to describe the same object.

Similarly, in relativity, when you describe an event in spacetime, you can use two different coordinate systems (one specific to each reference frame), but that doesn't affect where the event is located in spacetime.

Does that make sense to you?

9. Originally Posted by Jack_
you have enough information here to decide this problem.
You claimed you understood LT better than I do.

You explain it.

If you admit you do not understand it, then I will help.

Does the laser stop at x, or does it continue burning a path indefintely?
Is the vertical axis of your diagram a time axis?

10. Originally Posted by James R
Jack_:

So, since I am highly educated about relativity and it seems a little strange to me that you are using terminology that I have never come across in relation to relativity.
Well, so what. You learned a new phrase.

Originally Posted by James R
Can you please post an extract of a reference where Einstein claims two frames are co-located?
From above.
So, since I am highly educated about relativity
Wow.

Let M' be the mid-point of the distance A —> B on the travelling train. Just when the flashes 1 of lightning occur, this point M' naturally coincides with the point M, but it moves towards the right in the diagram with the velocity v of the train.
http://www.bartleby.com/173/9.html

Originally Posted by James R
Does that make sense to you?
No, we are dealing with light.

11. Originally Posted by Jack_
I am applying it to the coordinate system of the moving frame. This is the Minkowsky space.
No, you only transformed the x coordinate. The coordinate system of Minkowski space necessarily includes time coordinates as well.

Nice algebra and this is how the fast beating clock makes it appear resolved.
Clocks are irrelevant, but time is unavoidable. Yes, the problem is resolved by frame dependence of time.

You are introducing clocks here. The burn mark controls the destiny of the experiment not clocks.
Clocks are irrelevant, but time is unavoidable. The destiny of the experiment depends very much on time.

When the burn mark and O' are co-located there is a severe disagreement on the light path lengths.
Yes, there is. Just as there was severe disagreement on the length of the bike race length when the rider and the finish line were co-located.

12. Originally Posted by Pete

Does the laser stop at x, or does it continue burning a path indefintely?
Is the vertical axis of your diagram a time axis?
Does the laser stop at x, or does it continue burning a path indefintely
This does not matter for the problem.

LT in its most naked form runs inbto a contradiction.

Now, you are onto the worldline logic of geometry.

However, if you understand that, then you can understand a Cartesian diagram and imagine its motion in t.

Yes or no.

You see, the worldline logic does not confess the divergence in the light emission points and stacks those points up at a common origin which is false in reality.

13. Jack_:

Well, so what. You learned a new phrase.
I guess so. But it would be useful if you could try to stick to terminology used by physicists who are familiar with relativity. It makes discussing the topic easier.

Originally Posted by Jack_
Originally Posted by JR
Can you please post an extract of a reference where Einstein claims two frames are co-located?
Originally Posted by Einstein
Let M' be the mid-point of the distance A —> B on the travelling train. Just when the flashes 1 of lightning occur, this point M' naturally coincides with the point M, but it moves towards the right in the diagram with the velocity v of the train.
In this quote, Einstein talks about two points coinciding. What he means is that two points in space occupy the same location in space at one specific time measured in a particular frame of reference.

Einstein does not mention two entire frames being "co-located" in this quote. He only talks about two points. A reference frame has an infinite number of points. In fact, if the primed frame is moving relative to the unprimed frame in this example, then the coordinates of the two frames ONLY coincide at the points M and M' at this one particular instant, and NONE of the other coordinates in those frames match at that time.

Does that make sense to you?
No, we are dealing with light.
It doesn't matter. A flash of light can be treated the same way as any other object when it comes to events occurring in spacetime.

14. Originally Posted by Pete
No, you only transformed the x coordinate. The coordinate system of Minkowski space necessarily includes time coordinates as well.
Yes, it does. So does it with the diagram I offered. Necessarily, this imples a sequence of drawings. I can imagine that sequence, can you?

Originally Posted by Pete
Clocks are irrelevant, but time is unavoidable. Yes, the problem is resolved by frame dependence of time.
Guess what. You have not handled the geometry of my diagram. Why? You cannot. If so, do it. I want to see it.

Bring Rpenner here so I can correct him as well.

15. Originally Posted by Jack_
Yes, it does. So does it with the diagram I offered. Necessarily, this imples a sequence of drawings.
It's easier to use a spacetime diagram like Pete used earlier. That way, you avoid needing to imagine a sequence of drawings. You can just use one to specify all relevant events in spacetime and you can see it all neatly layed out in front of you.

Guess what. You have not handled the geometry of my diagram. Why? You cannot. If so, do it. I want to see it.
What are the two axes on your diagram? Pete has already asked you this question several times.

16. Originally Posted by James R
Jack_:

In this quote, Einstein talks about two points coinciding. What he means is that two points in space occupy the same location in space at one specific time measured in a particular frame of reference.
Say what?

Prove this.

Originally Posted by James R
Einstein does not mention two entire frames being "co-located" in this quote. He only talks about two points. A reference frame has an infinite number of points. In fact, if the primed frame is moving relative to the unprimed frame in this example, then the coordinates of the two frames ONLY coincide at the points M and M' at this one particular instant, and NONE of the other coordinates in those frames match at that time.

In his original thought experiment for LT, he co-located O and O' for the mirror experiment.

Are you claiming he was wrong?

Originally Posted by James R
It doesn't matter. A flash of light can be treated the same way as any other object when it comes to events occurring in spacetime.
You are wrong and weak at SR.

Here is how an object is treated.
See chapter 4.
http://www.fourmilab.ch/etexts/einstein/specrel/www/

Light on the other hand requires severe none time dilated adjustments to clocks that are illogical to work.

I have been showing this is false.

17. Originally Posted by James R
It's easier to use a spacetime diagram like Pete used earlier. That way, you avoid needing to imagine a sequence of drawings. You can just use one to specify all relevant events in spacetime and you can see it all neatly layed out in front of you.
Wrong, this spacetime diagram is for the weak minded and leaves off the diverging light emission points.
Therefore, it is non-scientific since it excludes known information.

18. OK, must go, later.

19. Jack_:

In this quote, Einstein talks about two points coinciding. What he means is that two points in space occupy the same location in space at one specific time measured in a particular frame of reference.
Say what?

Prove this.
You gave a link to the text yourself. All you have to do is read what Einstein says. For example:

Originally Posted by Einstein
Let M' be the mid-point of the distance A —> B on the travelling train. Just when the flashes 1 of lightning occur, this point M' naturally coincides with the point M, but it moves towards the right in the diagram with the velocity v of the train. If an observer sitting in the position M’ in the train did not possess this velocity, then he would remain permanently at M, and the light rays emitted by the flashes of lightning A and B would reach him simultaneously...
It is quite clear that M and M' are points or locations or positions in space, not entire reference frames.

Einstein does not mention two entire frames being "co-located" in this quote. He only talks about two points. A reference frame has an infinite number of points. In fact, if the primed frame is moving relative to the unprimed frame in this example, then the coordinates of the two frames ONLY coincide at the points M and M' at this one particular instant, and NONE of the other coordinates in those frames match at that time.
I am claiming that it is only possible for the coordinates of ONE point in two relatively-moving frames to coincide at any one instant of time.

I am not claiming it is impossible for two objects to occupy the same location in space.

In his original thought experiment for LT, he co-located O and O' for the mirror experiment.

Are you claiming he was wrong?
He co-located the origins O and O' of two coordinate systems (an unprimed one and a primed one) at one particular instant of time. Note that O and O', like M and M', are two points in space that coincide at one particular instant. At that instant, NONE of the other coordinates in the O and O' frames coincide (i.e. have the same numeric value at the same location in space).

You are wrong and weak at SR.
That's an empty assertion from you. Please don't descend to personal insults. If you can show that I am wrong, great. If not, insulting me won't help you.

Here is how an object is treated...
You link me to Einstein's entire first paper introducing special relativity. I have read it and am very familiar with its arguments. Which part in particular are you disputing?

20. Originally Posted by Jack_
Wrong, this spacetime diagram is for the weak minded and leaves off the diverging light emission points.

Therefore, it is non-scientific since it excludes known information.
Please draw me a spacetime diagram that shows the diverging light emission points. For clarity, please include the space and time coordinates of each of those points on your diagram.

Then we can compare to Pete's diagrams above and see where the difference lies.

Ok?